The present invention relates to platy potassium octatitanate, platy potassium hexatitanate, platy potassium tetratitanate, processes of producing them and friction materials.
Potassium octatitanate (K2O.8TiO2), potassium hexatitanate (K2O.6TiO2) and potassium tetratitanate (K2O.4TiO2) are generally produced in the form of fibrous compounds and widely used as resin reinforcers and friction materials for their superior crystal strength and high heat-insulating abilities.
However, conventional potassium octatitanate, potassium hexatitanate and potassium tetratitanate, because of their fibrous form, suffer from the following problems: they are bulky; they exhibit poor flowability; and they tend to get stuck on a wall of a feed passage during manufacture to eventually block it. In the resin reinforcer application, they show insufficient reinforcing performances against the force exerted in a direction of torsion. Further in the friction material application, it has been demanded that they are provided in the platy form advantageous to insure a high effect at frictional surfaces.
However, potassium octatitanate, potassium hexatitanate and potassium tetratitanate have not been provided in the platy form up to date, due to their favored crystal growth mechanism by which they are crystalized into the fibrous form.
It is an object of this invention to provide platy potassium octatitanate, platy potassium hexatitanate and platy potassium tetratitanate, processes for producing them and friction materials utilizing them.
The term xe2x80x9cplaty potassium titanatexe2x80x9d will be hereinafter used collectively in describing the matters common to platy potassium octatitanate, platy potassium hexatitanate and platy potassium tetratitanate.
The platy potassium titanate of the present invention is characterized as having a mean major diameter of 1-100 xcexcm and an aspect ratio of 3-500.
The process of producing the platy potassium titanate is characterized in that platy titanate is immersed in a potassium hydroxide solution and subsequently calcined.
Examples of useful platy titanates include those obtained by subjecting platy magnesium potassium titanate or platy lithium potassium titanate to an acid treatment.
In the production process of the present invention, a calcination temperature is preferably maintained within the range of 400-700xc2x0 C., more preferably within the range of 400-650xc2x0 C., further preferably within the range of 450-650xc2x0 C., further preferably within the range of 500-650xc2x0 C. for the case of platy potassium octatitanate. In the case of platy potassium hexatitanate, it is preferably maintained within the range of 600-800xc2x0 C. In the case of platy potassium tetratitanate, it is preferably maintained within the range of 700-800xc2x0 C.
The friction material of the present invention is characterized as containing the platy potassium titanate as a friction control agent. Preferably, the platy potassium titanate is contained in the friction material in the amount of 3-50% by weight.